Wiring Substrate With Projection For Finer Patterning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing wiring substrates face challenges in forming finer wiring due to thickness and unevenness in the conductive layers formed by copper foils, seed layers, and copper plating films.
Innovation Solution
A wiring substrate with a flexible insulation substrate and through wirings that include a projection extending along the lower surface of the second wiring layer, formed using electrolytic plating with a copper foil as a power feeding electrode, allowing for finer patterning and uniform thickness of the wiring layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copper foils, seed layers, and copper plating films are used to form conductive layers, then wiring layers can be formed with sufficient thickness and conductivity, but the thickness and unevenness in thickness of the conductive layer hinder the formation of fine wiring
Solution Approach 1:
The conductive layer is segmented into two distinct parts: a thin through wiring (formed by electrolytic plating) that provides electrical connection, and a separate copper foil wiring layer that provides current carrying capacity. This segmentation allows the through wiring to be formed with high precision and uniform thickness, while the copper foil handles the thickness requirement for conductivity.
Solution Approach 2:
The conventional sequence is inverted: instead of forming a thick conductive layer first and then patterning it, the patent first forms a thin through wiring by electrolytic plating, and then forms the copper foil wiring layer on top. This inversion allows precise control of the through wiring thickness while the copper foil is applied subsequently to achieve the required current carrying capacity.
2Reliability
If through holes are formed in the insulation layer with copper foils and seed layers, then via wirings can be formed to connect upper and lower wiring layers, but the existing structure transmits stress and thermal expansion differences that cause defects
Solution Approach 1:
The projection of the through wiring is designed to extend locally beyond the through hole on the lower surface, creating a stress-distributing structure. This local extension allows the through wiring to bridge and distribute stress over a larger area, reducing stress concentration at the through hole boundaries and preventing defects caused by thermal expansion differences.
3Manufacturing precision
If electrolytic copper plating is performed using seed layer as power feeding electrode, then via wirings with copper plating film are formed, but the process complexity and manufacturing difficulty increase
Solution Approach 1:
The copper foil itself serves as the power feeding electrode for the electrolytic plating process. The copper foil is positioned to extend beyond the through hole, and the electrolytic plating is performed using this copper foil as the anode. This self-service approach eliminates the need for separate external power feeding electrodes and complex masking structures, simplifying the manufacturing process while maintaining precise control over through wiring formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the formation of finely patterned and uniformly thick wiring layers with improved connection reliability and reduced stress transmission, facilitating the integration of electronic components without defects from thermal expansion differences.
Implementation Method 1
forming through wiring in the through hole by performing electrolytic plating using the first metal foil as a power feeding electrode
Data Source
AI summary
A wiring substrate includes a flexible insulation substrate, a first wiring layer formed on an upper surface of the insulation substrate, a second wiring layer formed on a lower surface of the insulation substrate, and through wiring bonded to the first wiring layer and the second wiring layer and formed in a through hole extending through the first wiring layer, the insulation substrate, and the second wiring layer. The through wiring includes a projection that extends along a lower surface of the second wiring layer located outside the through hole. An upper surface of the through wiring is flush with an upper surface of the first wiring layer.